It is not unusual for consumers of certain beverages, foods and medicines to notice a lingering flavor after swallowing. This could be a sense of heat from a spicy ethnic dish, or a very disagreeable bitter flavor after swallowing a liquid cough syrup. Some people may experience a chemical taste after consuming a diet beverage, while others may notice a pleasant smoky or buttery flavor after sipping gourmet coffee. These are all examples of a phenomenon known as an aftertaste.

In some cases, an agreeable aftertaste can be a good thing. Professional taste-testers of gourmet wines and coffees, for example, evaluate the aftertaste of a product for such qualities as smokiness, smoothness or longevity. A pleasant aftertaste, also known as finish, is considered a positive element of wines and coffees. Some beverages may have little to no aftertaste, or one that is very short-lived or unpleasant. A gourmet beverage's finish or aftertaste often depends on how long it lingers on the drinker's taste buds.

Under other circumstances, however, an aftertaste may be considered a bad turn of culinary events. Spicy ethnic foods may feature spices with a slow burn effect, but those lingering spices often create an unpleasant aftertaste until the palate is completely cleansed. Other ingredients such as cooking wine or acidic sauces could also leave an unpleasant aftertaste, especially if the diners are not accustomed to such strongly flavored dishes.

Perhaps the most noticeable example of an aftertaste occurs with artificial sweeteners. Many consumers of diet soft drinks and other products made with sugar substitutes complain of a noticeably bitter aftertaste immediately after swallowing. Even sugar substitutes created from sugar, such as Splenda®, can leave a chemical aftertaste. Some consumers do become accustomed to the aftertaste after repeated use, but for others the bitter or unpleasant aftertaste is considered a real deterrent. Producers of products containing sugar substitutes spend a great deal of time and money addressing the aftertaste issue, with varying levels of success among consumers.

Many liquid medications can also create an unpleasant aftertaste. The use of flavoring agents may help to mask some of the aftertaste, but many oral medications cannot be altered to eliminate it completely. Home remedies such as cod liver oil are often singled out for their extremely unpleasant aftertastes. Some people find the burning or medicinal aftertaste of alcohol-based mouthwashes to be quite disagreeable, while others may notice a strong aftertaste following a dose of cough medicine or oral antibiotics.